Among adenoma cases, no correlations were found for C-peptide, insulin or IGFBP-1 levels and either number of adenomas (r = 0.03, p = 0.65; r = 0.004, p = 0.96; r = 0.06, p = 0.41, respectively) or adenoma size (r = −0.05, p = 0.50; r = 0.14, p = 0.06; r = −0.02, p = 0.80, respectively). Here, INS is linked to adenoma.